This invention relates in general to fluid seals, and more particularly to static gaskets for various encapsulating covers and especially fuel cells.
A fuel cell is an electrochemical energy converter that includes two electrodes placed on opposite surfaces of an electrolyte. In one form, an ion-conducting polymer electrolyte membrane is disposed between two electrode layers to form a membrane electrode assembly (MEA). The MEA is used to promote a desired electrochemical reaction from two reactants. One reactant, oxygen or air, passes over one electrode while hydrogen, the other reactant, passes over the other electrode. The oxygen and hydrogen combine to produce water, and in the process generate electricity and heat.
An individual cell within a fuel cell assembly includes a MEA placed between a pair of separator plates. The separator plates are typically fluid impermeable and electrically conductive. Fluid flow passages or channels are formed adjacent to each plate surface at an electrode layer to facilitate access of the reactants to the electrodes and the removal of the products of the chemical reaction. In such fuel cells, resilient gaskets or seals are typically provided between the faces of the MEA and the perimeter of each separator plate to prevent leakage of the fluid reactant and product streams. Since the fuel cell operates with oxygen and hydrogen, it is important to provide a seal that not only seals well against hydrogen, oxygen and water, but that will seal well as the temperature changes due to the heat that is given off during fuel cell operation. To assure a good seal, bolts or other clamping mechanisms are used to maintain a compression load between the separator plates. This adds to the number of components in the assembly as well as making the assembly process more time consuming.
Thus, it is desirable to have a fuel cell with components that are relatively easy to assemble, while assuring the proper sealing for the finished assembly. And, in particular, it is desirable to have a fuel cell where the individual cells employ a minimum number of parts to assemble, while maintaining the proper compression load on the seal to assure the desired sealing characteristics for each individual cell.